(167h) Dynamic Control of Gold Nanoparticle-Conjugated DNA Origami Templates

Fabrication of nano-sized electronic and photonic devices through lithographic techniques is becoming increasingly challenging and energy intensive. Additionally, these methods are primarily confined to 2D surfaces and often do not include dynamic components that can reconfigure in response to external stimuli. Bio-inspired assembly through molecular recognition, such as base pairing interactions between deoxyribonucleic acid (DNA) strands, can be exploited to create dynamic, as well as robust, 3-D platforms for the organization of nanoparticles (NPs). DNA origami platforms can be used to organize NPs in precise orientations and spacings in 2D and 3D, yielding tailored plasmonic interactions. In some cases, these templates can be dynamic, adopting new conformations in response to external stimulus and altering these interactions. However, using the gold standard strand invasion approach that relies on de/hybridization kinetics, the inherent actuation time scale for these structures ranges from minutes to hours. Heating can increase response kinetics; however, use of external energy input is limited by bulk heat transfer. Therefore, localized energy input is desired as a means to potentially provide faster dynamics. Properties of NPs, such as surface plasmon resonance, can be explored as a localized energy source. Current research is focused on a fundamental understanding of the impact of NPs on dynamics and conformations of DNA origami structures actuated using the energy responsive NPs.

Our present study employs DNA origami hinges with single stranded DNA overhangs on the hinge arms as a model system. The sequence of these overhangs is complementary to that of single stranded (ss)-DNA on modified gold NP (AuNP) surfaces. A comparative study was conducted between the conformations of a closed hinge with varying locations of ss-DNA on the hinge arm in the presence and absence of AuNPs and analyzed by Transmission Electron microscopy (TEM) to determine the free energy landscape. Additionally, actuation kinetics of two different actuation pathways, strand displacement and bulk heating, were compared. Kinetics was studied in the bulk phase using fluorescence spectroscopy to analyze a Forster Resonance Energy Transfer (FRET) reporter system that indicated both NP binding and hinge closure. These results provided a comprehensive understanding of mechanical energy stored in NP-DNA origami composites. Preliminary experiments were performed for a third actuation scheme, localized actuation of composites using laser excitation to plasmonically heat AuNPs. Future experiments are investigating kinetics of structures undergoing local, plasmonic heating utilizing an in-house two source fluorometer instrument with separate excitation and modulation sources. This research could lead to higher order NP-DNA origami composites, that can store and release energy in response to light, with potential applications in nanophotonics.